This invention relates to microhollow cathode discharge devices and to microfluidic devices and more particularly to structures and methods of integrating the devices.
In gas and liquid sample analysis, capillary electrophoresis, blood chemistry analysis and analytical chemistry, smaller dimensions of capillaries often provide improved performances in throughput, speed, and reduced production or analysis costs (e.g. less reagents, smaller sample size, etc.). More recently, miniaturized planar separation systems (e.g. total microanalysis systems or lab-on-a-chip) have been fabricated by micromachining or microlithographic techniques in silicon, glass, and plastics. See for example Harrison D. J. et al., Science, 1993, 261, 895.
Although many separation systems have been demonstrated on-chip, there are only a few approaches to having on-chip optical detection systems reported into the literature. To date, epifluorescence detection external to a chip is commonly used for large channels of a few hundreds of microns in cross-section but there are needs for more sensitive optical detectors capable of measuring the passage of a small number of molecules in narrower channels. There are advantages to develop techniques to form channels with dimensions possibly smaller than the persistence length of a DNA polymer in order to extend the molecular strand to map its sequence. Single molecule manipulation will require high spatial resolution near-field optical probes requiring to go to some form of non-propagating evanescent mode. See for example, U.S. Pat. No. 5,623,339, entitled xe2x80x9cInterferometric Measuring Method Based on Multiple Sensingxe2x80x9d and U.S. Pat. No. 5,623,338, entitled xe2x80x9cInterferometric Near-Field Apparatus Based on Multiple Sensingxe2x80x9d, incorporated herein by reference. Although narrow apertures can be easily formed in various evaporated metallic films on a transparent substrate combined with a microchannel, it is very challenging to place a light source directly on-chip.
Accordingly it is highly desirable to provide new and improved integrated microhollow cathode discharge, for example as a light source, and microfluidic devices and methods of fabrication